The present invention relates to a wound type common mode choke coil used for various electronic equipment.
Conventionally, wound type common mode choke coils have been used in electronics, having a plurality of electrode layers disposed separately around the circumferential surface of one or both collar portions of a magnetic core, a pair of coil conductors wound around the winding core portion of said magnetic core by bifilar winding or the like, each terminal being conductively connected to each electrode layer of the collar portion by soldering, heat press fitting or the like and, further, the outer circumference of the wound coil conductor being coated with insulation coating layer.
In addition, a substantially closed magnetic circuit structure is commonly used having a winding around a coil conductor and a plate magnetic core coupling placed between both collar portions of the magnetic core as magnetic shield. Gluing with adhesive is used to adhere the plate magnetic core on the circumferential surfaces of both collar portions to reduce leak magnetic flux and improve the impedance characteristics.
In previous vertical disposition type wound type common mode choke coils, four terminal electrodes are disposed at predetermined intervals from the circumferential surface of the collar portion at the bottom side to the end face, i.e., where vertical mounting of the winding core portion of the magnetic core is desired. In horizontal disposition type choke coils, the four terminal electrodes are generally separately disposed two by two at both collar portions where the winding core portion of the magnetic core is parallel to the mounting substrate.
As mentioned above, there are both vertical disposition type, and horizontal disposition type devices (for vertical and horizontal mounting) for the winding core portion of the wound type common mode choke coil of the prior art, the horizontal disposition type being preferable when desiring reduction of the substrate mounting height. In this respect, the structure wherein the magnetic shield is obtained by adding the aforementioned plate magnetic core between the collar portions of the magnetic core is increased in height by the thickness of the plate magnetic core plate, so that the structure is undesirable when desiring a reduction in the height of the component mounted on a substrate.
From the viewpoint of ease of handling during the mounting process on the substrate, as well as reliability, a rectangular parallelepiped shaped tip shape wherein the insulation coating layer is armored to the outer circumference of the coil in such a way as to fill a concave area between both collar portions according to the square shape of the collar portion, is undesirable.
In addition, with conventional common mode choke coils, it is necessary to improve the common mode impedance characteristics through an enhanced binding by densely winding a pair of coil conductors by, for instance, bifilar winding, and at the same time, to possibly decrease the normal mode impedance. In this respect, it is preferable to armor the entire outer circumference of the pair of coil conductors wound around the winding core portion with a non-magnetic insulation coating layer for reducing the normal mode impedance. In contrast, with respect to reducing the leak magnetic flux due to the magnetic shield, it is preferable to obtain a closed magnetic circuit structure by coupling both collar portions of the choke coil with a magnetic body, wherein a substantially closed magnetic circuit structure is formed.
Further, with conventional devices, in a resin sealing process of the insulation coating layer, problems arise concerning appearance and reliability, as an excess of the resin armored to the outer circumference of the coil inevitably flows over the circumferential surface or end face of the collar portion form burr. This exposed burr is undesirable from the viewpoint of appearance, and must be removed by barrel polishing. However, during barrel polishing, a portion of the device from the outer circumference of the coil conductor to the conductive connection portion between respective terminals of the coil conductor and the electrode layer may be exposed, and the exposed portion may be easily damaged.
It is an object of the present invention to solve the aforementioned problems found in the conventional wound type common mode choke coils, and to improve the quality (reliability, characteristics, appearance, and the like) thereof.
In order to solve the above aforementioned problems, the present invention provides, in a first embodiment, a wound type common mode choke coil having a magnetic core, the magnetic core having a winding core with two ends and a square collar portion disposed respectively at each of the ends of the winding core, a circumferential surface on each collar portion, a groove portion disposed around the circumferential surface of each collar portion from the winding core side to the end face side of the collar portion;
a plurality of first electrode layers disposed separately at least around the circumferential surface of each collar portion of the magnetic core;
a pair of coil conductors wound around the winding core portion of the magnetic core, each of whose respective terminals are respectively conductively connected to the first electrode layer of each collar portion;
a non-magnetic first insulation coating layer disposed so as to integrally coat the outer circumference of the pair of coil conductors wound around the winding core portion of the magnetic core;
a second insulation coating layer armored/coated on the whole outer circumference of the first insulation coating layer, the second insulation coating layer containing magnetic powder of the winding core portion, and disposed according to the square shape of the collar portion from a concave area located between both collar portions to the groove portion of each collar portion of the magnetic core; and
a second electrode layer coating from the groove portion on which the second insulation coating layer of the circumferential surface of each collar portion of the magnetic core is disposed to the first electrode layer. Further to the first embodiment of the wound type common mode choke coil, of the first embodiment of the present invention above, the conductive connection portion of respective terminals of the pair of coil conductors and the first electrode layer is disposed in the groove portion on the circumferential surface of the collar portion.
In a second embodiment of the present invention, a wound type common mode choke coil is provided, wherein the first insulation coating layer coats from the outer circumference of the pair of coil conductors wound around the winding core portion of the magnetic core to the conductive connection portion E of respective terminals of the coil conductors and the first electrode layer.